1. Field of the Invention
This invention relates to a radio receiver with a built-in telescope.
2. Description of the Related Art
Some watchers of a sport game or a horse race often use a telescope as they listen to on-the-spot broadcast from a radio broadcasting station. It is however highly cumbersome to carry both the telescope and the radio receiver to the sports arena or a racecourse. Since it is necessary to focus the telescope and to tune in the radio receiver simultaneously, one may fail to view or hear a critical scene. In addition, one may fail to grasp a fairly large number of articles and allow them to drop on the ground or floor. Thus there exists a demand for telescope-radio receiver assembly in which a telescope and a radio receiver are unified into an integral unit.
In a telescope, since distortion in a lens barrel fitted with a lens leads to problems such as warped image or moire pattern, telescope components including the lens barrel are fabricated with sufficient mechanical strength and precision by metal die-casting. Thus the conventional telescope tends to be increased in weight.
On the other hand, portable radio receivers are generally classed into two-band type receivers capable of receiving FM broadcast and AM broadcast, and three-band type receivers capable of receiving FM broadcast, AM broadcast and short-wave broadcast. For clear reception of electrical waves for each such broadcast, an antenna is required, while an earphone cord is simultaneously employed as an antenna for receiving the FM broadcast. As an AM broadcast reception antenna, an extensible rod antenna or an enclosed type ferrite bar antenna is employed. In a portable pocket-sized radio receiver, a ferrite bar antenna is in widespread use because it does not catch the apparel and moreover is unprotrusive.
Such ferrite bar antenna has a high directivity, while its reception sensitivity is significantly lowered if the path along which the electrical waves reach the antenna is obstructed by an electrically conductive member, such as a metal member. Thus, sufficient attention needs to be exercised as to the disposition of the ferrite bar antenna in designing a radio receiver.
Since the portable radio receiver and the telescope have the above-described characteristics, if these are simply combined into a sole telescope-radio receiver device, it is increased in size and weight and difficult to use as a portable type device. Since the radio receiver has only poor reception sensitivity, the device may hardly be put to practical application. Above all, the lens barrel fabricated by metal diecasting has a dual barrier wall, that is inner and outer barrier walls, with respect to the ferrite bar antenna, so that it deteriorates reception sensitivity significantly.